Advanced Coffee Making

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ACM Real World Applications

ACM 7.02 – Equipment Testing

Equipment Testing

Always Aim High

The asymptote of extraction — higher is more consistent than somewhere in the middle.

The Folio of Descartes: A famous example of an asymptote
By Inductive load — Own work, Public Domain,

At BH, we have a heuristic: equipment that promotes higher extraction is better. Imagine the dotted blue line in this graph (which is an asymptote) represents perfect coffee equipment or the ideal brewing scenario. New innovations get us closer to ideal results but we accept that nothing is perfect.


When the specialty coffee industry made movements towards universally adopting the Mahlkoenig EK43, it wasn’t just because it was popular. This particular grinder increased the average extraction yield of non-espresso coffees by 2–4% and espresso coffees by 2–6% when compared with standard equipment. Many coffee roasters reported being able to taste more in their resultant brew profiles and baristas found they had greater control over their recipes. Cafe owners discovered not-insignificant commercial benefits.

Industrial grinders, like roller mills, can easily achieve 26% extraction if the coffee is roasted well. The clarity and transparency of brews made with these (very expensive and large) grinders are incredible. This also demonstrates that higher extraction yields — when done right — are certainly an improvement.


Moving from a curved to a flat-based tamper makes an instant and noticeable gain in extraction yield. The rationale behind why tampers were made as convex was that because most channelling occurs between the side of the basket and the coffee, banking more coffee grinds up against the edges of the basket would add resistance to these areas. After the advent of the Coffee Refractometer, it was made clear that this approach let to lower average extraction yields.


Good distribution of grinds in a filter paper or espresso basket is crucial for the achievement of delicious taste. If the grinder funnel delivers a lopsided mass of grinds,